Exercise Has Modest Effect on Depression

Action Points

Note that this Cochrane meta-analysis found a modest beneficial effect of exercise on depression.

Be aware that the majority of studies included in the meta-analysis were methodologically flawed.

Exercise had a moderate effect on symptoms of depression in a meta-analysis, but the benefit diminished in an analysis limited to well-designed studies, investigators concluded.

When compared with no treatment or control interventions, exercise was associated with a treatment effect of -0.62, although many of the 35 trials included in the analysis had one or more biases or other faults.

An analysis limited to a half dozen methodologically sound studies yielded a treatment effect of -0.18, which was not statistically significant. Pooled data from trials that reported long-term follow-up showed a slightly larger effect of exercise, which was statistically significant.

"Our review suggested that exercise might have a moderate-sized effect on depression, but because of the risks of bias in many of the trials, the effect of exercise may only be small," the authors concluded. "We cannot be certain what type and intensity of exercise may be effective and the optimum duration and frequency of a program of exercise. There are few data on whether any benefits persist after exercise has stopped.

"The evidence also suggests that exercise may be as effective as psychological or pharmacological treatments, but the number of trials reporting these comparisons and the number of participants randomized were both small."

Simon Rego, PsyD, director of psychology training at Montefiore Medical Center/Albert Einstein College of Medicine in New York, told MedPage Today that the "finding that exercise may be as effective as psychological or pharmacological treatments is an important one, given that both psychological and pharmacological treatments each have their cons.

"For example, antidepressants require good adherence to be effective and, given that they may have adverse side effects and there is typically a lag time between starting antidepressants and improvements in mood, some patients prefer an alternative treatment. And while the first-line psychological treatments such as Cognitive Behavioral Therapy (CBT) do not have adverse side effects, they do require access to a psychologist with expertise in delivering the treatment and sustained motivation to comply with the homework assignments, and some patients prefer an alternative due to the perceived stigma of seeing a therapist," Rego wrote in an email.

But he cautioned that the studies included in the analysis were small and "when studies were restricted only to those trials in which participants with a clinical diagnosis of depression were included, a separate review found no evidence of an effect of exercise. Thus, more research is needed before considering exercise a first-line treatment for depression in adults."

John E. Lewis, PhD, an associate professor at the University of Miami School of Medicine, noted that since exercise has a number of well-documented benefits to physical health, an exercise intervention was worth considering in subsets of patients.

"If a patient does not want to take medication or has found medication to be ineffective and/or did not benefit from psychological therapy, then exercise may offer a closely effective alternative," Lewis wrote in an email. "Because many people suffer from treatment-resistant depression, exercise may provide an alternative for those patients in particular. Given the systemic and widely-recognized benefits of exercise, it makes sense that exercise could be an effective way to counteract the effects of depression. With virtually no risk of serious adverse event, exercise can be utilized without fear."

Depression most often is treated with antidepressants, psychological therapy, or a combination of the two. Drug therapy can cause side effects that some patients find unacceptable, adherence can be a problem, and the drugs often require several weeks to produce a noticeable effect on symptoms, the authors noted in the background to their analysis.

Moreover, some patients might prefer alternatives to drugs and psychotherapy. Interest in alternatives has led to evaluation of interventions such as music therapy, light therapy, acupuncture, relaxation, and exercise, among others.

Mead and colleagues performed a review of exercise as defined by the American College of Sports Medicine: "planned, structured, and repetitive bodily movement done to improve or maintain one or more components of physical fitness."

Investigators searched multiple databases for randomized trials of exercise interventions for depression in adults, as compared with no treatment or to a comparator intervention. They identified 39 trials involving 2,326 patients, and 37 of the studies were suitable to include in the meta-analysis.

Analysis of studies comparing exercise to no treatment or a control intervention yielded a standardized mean difference (SMD) between groups of -0.62 (95% CI -0.81-minus 0.42), indicating a moderate clinical effect. The authors found that the studies exhibited a moderate degree of heterogeneity.

Mead and colleagues performed a separate analysis of six trials (464 participants) that had adequate allocation concealment, intention-to-treat analysis, and blinded outcomes assessment. The pooled SMD for this subgroup of well-designed trials was -0.18 (-0.47-0.11), which did not achieve statistical significance.

Analysis of eight trials (377 participants) with long-term follow-up produced an SMD of -0.33 (95% CI -0.63-minus 0.03), indicating a small treatment effect.

One trial involving 18 patients compared exercise and light therapy and found the former more effective (SMD -6.40, 95% CI -10.20-minus 2.60).

On the basis of their findings, Mead and colleagues recommended research aimed at identifying specific types of exercise that offer the greatest clinical benefit, as well as the number and duration of exercise sessions associated with the greatest benefit. They also called for clinical trials to confirm the finding that exercise is as effective as psychological and pharmacological treatment of depression.

Mead disclosed that she receives royalties for a course she developed and for a book she wrote about exercise after stroke.

Reviewed by F. Perry Wilson, MD, MSCE Instructor of Medicine, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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